DEA-C01 Data Operations and Support Practice Question
A company uses Amazon S3 to store large CSV files and runs Amazon Athena queries on them. The queries are becoming slower as data grows. A data engineer suggests converting the files to Apache Parquet format and partitioning the data. What is the primary benefit of converting to Parquet?
⚠ Common exam trap
Many exam-takers confuse the general benefits of Parquet (compression, schema evolution, nested data) with the primary performance benefit for Athena, which is columnar pruning reducing scanned data.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Parquet stores data in a columnar format, reducing the amount of data scanned per query.
Parquet is a columnar storage format that stores data by columns rather than rows. When Athena queries only a subset of columns, it can read just those columns from disk, drastically reducing the amount of data scanned per query. This directly addresses the performance slowdown because Athena charges by data scanned, and less scanning means faster queries and lower costs.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Parquet allows schema evolution without rewriting files.
Why it's wrong here
Schema evolution is not a primary benefit of Parquet.
- ✗
Parquet supports nested data structures that CSV cannot.
Why it's wrong here
While true, it is not the primary benefit for query speed.
- ✓
Parquet stores data in a columnar format, reducing the amount of data scanned per query.
Why this is correct
Columnar storage minimizes I/O by reading only relevant columns.
- ✗
Parquet is compressed by default, reducing storage costs.
Why it's wrong here
Compression is a benefit but not the primary query performance benefit.
Quick reference
AWS S3 Storage Class Comparison
| Storage Class | Min Duration | Retrieval | Use Case |
|---|---|---|---|
| S3 Standard | None | Immediate | Frequently accessed data |
| S3 Standard-IA | 30 days | Immediate | Infrequent access, rapid retrieval |
| S3 One Zone-IA | 30 days | Immediate | Non-critical infrequent data |
| S3 Intelligent-Tiering | None | Immediate–hours | Unknown or changing access patterns |
| S3 Glacier Instant | 90 days | Milliseconds | Archive with instant retrieval |
| S3 Glacier Flexible | 90 days | Minutes–hours | Archive, flexible retrieval |
| S3 Glacier Deep Archive | 180 days | Hours | Long-term compliance archive |
Go deeper
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DEA-C01 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DEA-C01 exam.